Most fuel injectors include one or more electronically controlled valves that open and close various fuel passageways to facilitate control over fuel injection events. One class of such fuel injectors is typically identified as a mechanically actuated, electronically controlled unit injector (MEUI) which utilize an electronically controlled valve to precisely control a timing at which fuel in the fuel injector becomes pressurized. In particular, a rotating cam periodically advances a plunger to pressurize fuel in a fuel pressurization chamber, but pressure does not rise until a spill valve is closed. If a spill valve is closed during a plunger stroke, fuel pressure quickly rises followed by opening of a nozzle outlet to perform an injection event. A spill valve for such an injector is shown, for example in co-owned U.S. Pat. No. 6,349,920. Later evolutions of the MEUI fuel injector added a second electronically controlled valve to control the opening and closing of the nozzle outlet somewhat independently of the fuel pressurization event accomplished through the spill valve.
The phenomenon known as cavitation can sometimes arise at unexpected locations within a fuel injector. Furthermore, cavitation damage can in some cases potentially lead to premature fuel injector failure rather than simple wear and tear on the various inner surfaces defining the fuel passageways through the fuel injector. One common location where fuel injectors receive cavitation damage is on the valve members. The collapse of cavitation bubbles may eventually erode an annular surface on the valve member and may affect its operation, the operation of the fuel injector, and the operation of the engine. Cavitation erosion is also undesirable because it produces small metallic particles that can cause scuffing and seizure in moving parts of a fuel system.
Unfortunately, modeling fluid systems to predict the occurrence of cavitation, as well as potential magnitudes of damage and their respective locations due to cavitation has proven to be extremely difficult. Thus, a computer aided design strategy for avoiding some cavitation damage problems is not realistic as the modeling tools available to simulate various different design shapes and evaluate the same for potential cavitation damage are not capable of accurately and reliably predicting some cavitation damage problems. Thus, engineers are sometimes left with exploiting simple trial and error in various design alternatives in order to address potential cavitation damage issues.
The present disclosure is directed to overcoming one or more of the problems set forth above.